This invention relates to apparatus for automatically testing fluid samples such as blood, and more particularly to an automatic sampling system that receives a continuous linkage of any preselected number of test tubes for continuous, unattended analysis of the test tube contents.
In almost routine fashion, the body fluids and tissues of millions of individuals are submitted for testing each day to assess various characteristics of their body chemistry. The tests, which are conducted in hospitals, independent laboratories and doctors' offices, are often used to supplement a medical judgment, as well as provide data for other determinations. An increasing proportion of such tests are used to detect the presence of fatal diseases such as AIDS, and to screen for illicit drug use.
Known automated and computerized test apparatus can perform multiple test analyses of blood chemistry, determine the blood type and Rh factor as well as screen for syphilis and German measles. Examples of apparatus and processes for carrying out automatic blood testing are shown in U.S. Pat. Nos. 3,740,143; 3,741,875 and 4,487,700.
Many known test apparatus for testing fluid samples require manual feeding of open test tubes, necessitating the presence of an operator or technician during the performance of such tests. An important function of an operator in addition to introducing a fluid sample into a test apparatus, is to mix the sample just before it is introduced.
Thus, the development of automatic feed systems for test apparatus of the type described has become a major goal of the testing industry.
In response to this problem, U.S. Pat. No. 4,609,017 discloses a transport system for automatically transporting sealed test tubes and mixing the test tubes. In accordance with the transport system, a set number of test tubes are lined up in a rack and a plurality of such racks are stacked by an operator in the test apparatus. Each rack is automatically shifted in successive order onto a conveyor belt which moves in stepwise fashion to align a respective test tube in the rack with an aspirator that draws a fluid sample from the test tube. The conveyor belt is supported on a table that is rocked during each advancing step to mix the contents of the test tubes.
When a test tube is aligned with the aspirator, a push rod projects the test tube out of the rack against the aspirator needle. After aspiration is completed, a stripper bar retracts the protracted test tube back into the rack. The conveyor then moves another step to align the next test tube in the rack with the aspirator needle. When the complete line of test tubes in the rack have been aspirated, the rack is shifted by the conveyor into a storage space in the apparatus for eventual removal by an operator.
A primary disadvantage of the rack feed arrangement is the limited capacity in the test apparatus of stacking space for accommodating the incoming racks. Another disadvantage is that the finished racks remain stored in the apparatus until their removal by an operator. A further disadvantage is the racks are held in place on the conveyor by frictional contact between the rack and the conveyor. Thus, any slippage between the rack and conveyor will upset the indexing system movement that aligns the test tubes with the aspirator with each stepwise movement of the conveyor. Such slippage may occur when a test tube is protracted from the rack with a push rod to engage the aspirator. The push rod can upset the position of the rack on the conveyor and require the intervention of an operator to correct such malfunction. Similar slippage can occur when the stripper bar is used to retract the test tube into the rack. A still further disadvantage is that the test tube racks must be elevated onto and off the conveyor belt, thus requiring a separate elevator system. Still another disadvantage is that all test tubes in the rack must be of the same size.
A continuous feed arrangement for test tubes, as shown in U.S. Pat. No. 3,521,785, discloses test tubes connected together in chain-like fashion by using the test tubes to form the joints of the chain. Removal or breakage of one test tube will cause a break in the chain. In addition, this device does not permit the mixing of a given number of test tubes in the chain which are in proximity of a sampling station of a test apparatus.
It is thus desirable to provide an automatic test apparatus having an automatic feed system which can feed an unlimited number of test tubes in continuous fashion to a sampling station of the test apparatus, continuously identify each test tube that is being sampled, and continuously deposit the finished test tubes in a collection area. It is also desirable that the continuous feed system mix a predetermined number of the test tubes just before they are tested and that the contents of the test tube be sampled or withdrawn without moving the test tube from its transported position.